Contrasting background display

ABSTRACT

Contrasting background for display of letters, numbers, or other indicia is provided by using a sheet of louvered material in which thin parallel opaque louvers are set in a transparent matrix at an angle to the faces of the sheet. Light is made to pass through the louvered sheet generally parallel to the louvers at an angle to the faces of the sheet to display indicia defined by a differential pattern of light diffusive and transparent areas. The light diffusive areas direct a portion of the incident light to an observer while the louvers are seen in contrast through the transparent areas.

United States] 4 XFQ 3961532138 Cooper CONTRASTING BACKGROUND DISPLAYIrvin J. Cooper, White Bear Township, Ramsey County, Minn.

Minnesota Mining and Manufacutring Company, St. Paul, Minn.

Filed: Apr. 13, 1970 Appl. No.: 27,843

Lake

lnventor:

Assignee:

References Cited UNITED STATES PATENTS 1/1936 Terwilliger ..40/132 EApr. 4, 1972 Primary Examiner-Robert W. Michell AssistantExaminer-Richard Carter Attorney-Kinney, Alexander, Sell, Steldt &Delahunt [5 7] ABSTRACT Contrasting background for display of letters,numbers, or other indicia is provided by using a sheet of louveredmaterial in which thin parallel opaque louvers are set in a transparentmatrix at an angle to the faces of the sheet. Light is made to passthrough the louvered sheet generally parallel to the louvers at an angleto the faces of the sheet to display indicia defined by a differentialpattern of light diffusive and transparent areas. The light diffusiveareas direct a portion of the incident light to an observer while thelouvers are seen in contrast through the transparent areas.

3 Claims, 2 Drawing Figures 0a in ie/11W PATENTEDAPR 41912 3,653,138

FIG. 3

INVENTOR.

[R V/N J COOPER Mama/(2AM ATTORNEYS CONTRASTING BACKGROUND DISPLAY Thisinvention relates to display devices and particularly to display devicesin which a contrast is to be maintained between the article beingdisplayed and the background under both ambient and nighttime lighting.In addition this invention relates to display devices which are usefulfor providing the positive appearance of a photographic negative and forsigns and alphanumeric displays.

It is often difficult to demonstrate numerals by suitable backgroundwhich is in sharp enough contrast that is visible both by daylightincluding ambient lighting or under conditions of very low ambientlighting by transillumination and from behind. A suitable example wouldbe the exit signs in a moving picture theatre which must be visible bothwhen the lights are on and after the lights have been turned off.Another situation in which contrast is desired of somewhat similar typeis in viewing black and white picture negatives. ln this case in orderto see the positive the unexposed portion must appear black as it willin the print and the black part of the negative must appear in lightcolor. In other words, contrast is sought between the indicia that arepresent and the background.

It has now been found possible by using a louvered film to provide abackground which can be illuminated at an angle such that the lightpassing through is sufficient to illuminate a display in front of thefilm and yet at the same time does not illuminate the background aroundthat display. In addition, where desired, a colored filter may beprovided in front of the display so that the display is seen in colorother than that normal to it. The display may be of indicia or patternsin various desired forms. For example, it may be letters which aremounted directly on the louvered film, it may be a photographic negativewhich is placed in front of the film for viewing or it may be a nematicdisplay by dynamic scattering as described, for example, in U.S. Pat.No. 3,499,] 12.

Louvered films of the type which are useful for this purpose areprepared as described in the copending application of Frederick 0.Olsen, Ser. No. 660,754 filed on Aug. 15, 1967 and assigned to theassignee of this application, by the skiving of billets of alternatingclear and black or other colored sheets. It will be recognized that theskiving of a sheet in which the black planes are normal to the surfacewill give the wrong angles but by deformation it is possible to obtainsheets in which louvers are properly inclined. Such films can also beproduced by cutting from a block of material made with the desiredangles.

As indicated above the display material may be of any of several types.In each case a different embodiment of the invention is obtained. Two ofthese embodiments are explained by reference to the accompanyingdrawings in which:

FIG. 1 is a perspective view in section of a first embodiment of thepresent invention;

FIG. 2 is a perspective view in section of a second embodiment of thepresent invention. 7

The display of the present invention as illustrated in FIGS. 1 and 2includes a light source 10 and a sheet of louvered material 12.

The sheet of louvered material 12 comprises a transparent matrix 14 inwhich a plurality of generally parallel thin opaque louvers 16 are setat an angle to the faces of the sheet, the louvers 16 being spaced withopposed edges of adjacent louvers at least contacting a single planenormal to the faces of the sheet 12 to prevent transmission of lightstriking the sheet 12 perpendicular to the faces thereof. The sheet 12is preferably formed of a thermoplastic material, the matrix 14 beingtransparent and the louvers 16 being opaque. A process for producing alouvered structure with louvers normal to the faces of the sheet isdescribed in the aforementioned application of Frederick 0. Olsen, Ser.No. 660,754 as including the steps of placing alternating clear andpigmented thermoplastic disks on a shaft, heating the composite whileapplying pressure to form a billet and skiving the billet while heatingthe surface of the billet immediately before contact with the skivingknife to a temperature sufficient to permit softening of the polymer atleast to a depth'contacting the skiving knife. Inclination of thepigmented louvers to the faces of the sheet so that opposed edges ofadjacent louvers at least contact a single plane normal to the faces ofthe sheet may be produced by placing the perpendicularly louvered sheetbetween a pair of metal plates and heating the sheet while slowly movingone of the metal plates in the desired direction of louver inclination.Further inclination of the louvers 16 would then produce overlapping ofthe opposed edges of adjacent louvers which may be desired to assure theprevention of light transmission normal to the faces of the sheet 12. Byappropriate coloration of the disks prior to formation of the billet,the louvers 16 may provide any desired contrasting background for thedisplay as will be hereinafter described.

The light source 10 preferably comprises a cylindrical lamp 18positioned to one side of the sheet of louvered material 12 andextending parallel thereto, a semicylindrical reflector 20 adjacent thelamp 18 and a parabolic reflector 22. The parabolic reflector 22 ispositioned to cooperate with the semicylindrical reflector 20 to directlight produced by the lamp 18 into paths parallel to the planes of thelouvers through the matrix 14 of the louvered sheet 12 between thelouvers 16 and provide equal intensity illumination across the louveredsheet 12. r

The article to be displayed is positioned on the opposed side of thesheet of louvered material 12 from the light source 10 so as to beilluminated by light passing through the matrix 14 between the louvers16. An article to be displayed for use with the present inventionincludes a differential pattern of light diffusive and transparent areasdefining the indicia to be displayed. This may be accomplished byaffixing the light diffusive indicia directly to the opposed face of thesheet of louvered material 12 whereby the matrix 14 of the louveredsheet 12 provides a transparent background substantially surrounding theindicia. In this instance an observer positioned out of the path of thelight passing through the matrix 14 between the louvers 16 would observethe indicia due to the diffusion of the light by the indicia while thelouvers 16 will provide a visible contrasting background for theindicia. Thus, if the louvers 16 are black the indicia will appear inlight color on a black background. The louvers 16 may have any colorcontrasting with the coloration of the indicia and a colored filtermaybe placed between the indicia and the observer to provide furthercoloration as desired. Such positioning of a colored filter providescontinuity of color contrast with both ambient and backlighting.

Referring now to FIG. 1 there is illustrated one embodiment of thepresent invention utilizing a black and white photographic negative 24as the article to be displayed. In this embodiment the louvers 16 arepreferably black to provide the proper background coloration. Lightpassing through the matrix 14 of the louvered sheet 12 between thelouvers l6 strikes the entire back surface of the negative 24. In theunimaged areas the negative 24 is transparent and the light rayscontinue their inclined path and are not seen by an observer 26. Lightstriking the imaged areas of the negative 24 is diffused by the indicia25 so that at least a portion of the light striking the imaged areas isdiffused and directed to the observer 26. With the black backgroundprovided by the louvers l6 and observable through the transparentunimaged areas, the light diffused from the indicia 25 on the negative24 makes them appear in light color on a black background as would apositive made from the negative 24.

Referring now to FIG. 2- there is illustrated a second embodiment of thepresent invention utilizing a nematic liquid crystal display device 28.Nematic liquid crystal displays are well known in the art and typicallyinclude a pair of spaced parallel transparent plates which supportelectrode strips on their adjacent faces. The space between the platesis filled with a nematic crystal composition of a type that exhibitsturbulent motion upon the application of an electric field whichproduces an electric current in the film. The display 28 is normallygenerally transparent and upon causing an electric current to flowthrough selected electrodes the liquid crystal layer becomes turbulentin selected areas and gives rise to scattering or diffusion of lightincident on that portion of the display. By proper selection of thecurrent flow, light diffusive indicia 29 are generated in the display28. In this embodiment the louvers 16 are preferably black and when thedisplay is backlit as illustrated and no indicia 29 are generated, thelight passes through the matrix 14 between the louvers 16 and continuesthrough the liquid crystal display 28 so that an observer 30 secs onlythe black background provided by the louvers 16. When indicia 29 aregenerated in the display 28 light striking the indicia 29 is diffused sothat portions thereof are directed to the observer 30. The indicia 29then appear in light color on the black background provided by thelouvers 16. This embodiment is also useful in instances where there isambient lighting during daylight hours since the generated indicia 29 indiffusing light will reflect a portion back to the observer 30 while theblack background provided by the louvers 16 will absorb light passingthrough the light transmissive areas of the display 28. This then is anexcellent display for use when it is desired to display indicia bothduring daylight and during periods of very low ambient lighting.

Having thus described the present invention, what is claimed is:

l. A display device comprising:

a sheet of louvered material having a plurality of generally parallelthin opaque louvers set in a transparent matrix at an angle to the facesof said sheet, said louvers being spaced with opposed edges of adjacentlouvers at least contacting a single plane normal to said faces toprevent transmission of light striking said sheet perpendicular to saidfaces,

a light source positioned to one side of said sheet of louvered materialto direct light through said matrix between said louvers along pathsgenerally parallel to said louvers, and

an article to be displayed positioned on the opposed side and parallelto said sheet of louvered material to be illuminated by radiation fromsaid light source passing through said matrix between said louvers, saidarticle including a differential pattern of light diffusive andtransparent areas defining the indicia to be displayed and saiddifferential pattern being at least partially of contrasting colorationto said opaque louvers so that said differential pattern is visible bothfrom ambient light and under illumination.

2. A display device comprising:

a sheet of louvered material having a plurality of generally parallelthin opaque louvers set in a transparent matrix at an angle to the facesof said sheet, said louvers being spaced with opposed edges of adjacentlouvers at least contacting a single plane normal to said faces toprevent transmission of light striking said sheet perpendicular to saidfaces,

a light source positioned to one side of said sheet of lou veredmaterial to direct light through said matrix between said louvers alongpaths generally parallel to said louvers, and

a nematic liquid crystal display device positioned on the opposed sideof and parallel to said sheet of louvered material to be illuminated byradiation from said light source passing through said matrix betweensaid louvers, said liquid crystal display device providing adifferential pattern of light diffusive and transparent areas definingthe indicia to be displayed visible both from ambient light and underillumination.

3. A display device comprising:

a sheet of louvered material having a plurality of generally parallelthin opaque louvers set in a transparent matrix at an angle to the facesof said sheet, said louvers being spaced with opposed edges of adjacentlouvers at least contacting a single plane normal to said faces toprevent transmission of light striking said sheet perpendicular to saidfaces, a light source positioned to one side of said sheet of louveredmaterial to direct light through said matrix between said louvers alongpaths generally parallel to said louvers, and

a dark and light photographic transparency positioned on the opposedside of and parallel to said sheet of louvered material to beilluminated by radiation from said light source passing through saidmatrix between said louvers so that under illumination the dark andlight areas of said transparency appear light and dark respectively.

1. A display device comprising: a sheet of louvered material having aplurality of generally parallel thin opaque louvers set in a transparentmatrix at an angle to the faces of said sheet, said louvers being spacedwith opposed edges of adjacent louvers at least contacting a singleplane normal to said faces to prevent transmission of light strikingsaid sheet perpendicular to said faces, a light source positioned to oneside of said sheet of louvered material to direct light through saidmatrix between said louvers along paths generally parallel to saidlouvers, and an article to be displayed positioned on the opposed sideand parallel to said sheet Of louvered material to be illuminated byradiation from said light source passing through said matrix betweensaid louvers, said article including a differential pattern of lightdiffusive and transparent areas defining the indicia to be displayed andsaid differential pattern being at least partially of contrastingcoloration to said opaque louvers so that said differential pattern isvisible both from ambient light and under illumination.
 2. A displaydevice comprising: a sheet of louvered material having a plurality ofgenerally parallel thin opaque louvers set in a transparent matrix at anangle to the faces of said sheet, said louvers being spaced with opposededges of adjacent louvers at least contacting a single plane normal tosaid faces to prevent transmission of light striking said sheetperpendicular to said faces, a light source positioned to one side ofsaid sheet of louvered material to direct light through said matrixbetween said louvers along paths generally parallel to said louvers, anda nematic liquid crystal display device positioned on the opposed sideof and parallel to said sheet of louvered material to be illuminated byradiation from said light source passing through said matrix betweensaid louvers, said liquid crystal display device providing adifferential pattern of light diffusive and transparent areas definingthe indicia to be displayed visible both from ambient light and underillumination.
 3. A display device comprising: a sheet of louveredmaterial having a plurality of generally parallel thin opaque louversset in a transparent matrix at an angle to the faces of said sheet, saidlouvers being spaced with opposed edges of adjacent louvers at leastcontacting a single plane normal to said faces to prevent transmissionof light striking said sheet perpendicular to said faces, a light sourcepositioned to one side of said sheet of louvered material to directlight through said matrix between said louvers along paths generallyparallel to said louvers, and a dark and light photographic transparencypositioned on the opposed side of and parallel to said sheet of louveredmaterial to be illuminated by radiation from said light source passingthrough said matrix between said louvers so that under illumination thedark and light areas of said transparency appear light and darkrespectively.